Radiodetector and process for making the same



Patented they 25, 7 UNITED TATES rnnnaarcx HENDEY, or rAssAIe,

ant Rossett- B. Eves/sou, or otirrou, new JERSEY.

RADIODETECTOR AND PROCESS FOR MAKING THE SAME.

No Drawing.

To all whom it may concern:

Be it known that we, Fnnunuror; H. HEN- our and RUssnLL B. EvnusoN, citizens of the United States, residing at Passaic and Clifton, respectively, county of Passaic, and State of New Jersey, have invented certain new and useful Improvements in Radiodetectors and Processes for Making the Same, fully described and represented in the following specification.

The present invention relates to a new radiodetector and process for making the same.

Heretofore various natural and artificial crystals have been used in radio apparatus as so-called detectors,- whose function is generally assumed to be that of rectifying the r'adiofrequency currents, to produce pulsator'y currents capable of actuating a telephone.

Such crystal detectors, however, have only been capable of use within relatively short distances of a transmitting station, and are readily put out of action by heavy static or heavy sparks at the detector device.

The main object of the presentinvention is to provide a new detector material which will be capable of use in place of the previously known so-called crystal detectors and which, when so used, will be capable of operation under usual working conditions, with more infrequent attention and readjustment of the cat-whisker or contact point, than with the present crystal detectors.-

Vith the above general object in view and some others which will appear from the description hereinafter, the invention consists in a detector comprising a substantially homogeneous ininture of lead sulphide and free lead, the lead sulphide comprising the principal ingredient. The invention also comprises a process of inakii'ig. the above material. Finally, the invention includes the combination with the detector comprising said mixture of a catwvlrisker or detector point of Zinc or aluminum, most advantageously in the form of a narrow strip of metal whose end may rest flat on the detector. c

The detector material has the great advantage that it may be forced into a contact-cup, such as is frequently used with crystal detectors, under pressure, and thereby will be compacted in the cup so as to Application filed August 3, 1922.

Serial No. 579,497.

make a good electrical connection with the cup.

The proportions of lead sulphide and free lead may be varied to a considerable-extent, but in practice it has been found that the best results have been obtained with material comprising about 93% lead sulphide and about 5 to 7% of free lead. With this material there is usually a slight amount of lead sulphate, some free sulphur and a small amount of iron oxide, but these are considered to be merely impurities.

Two samples of material which were particularly good embodiments of the invention, when subjected to chemical analyses by the usual laboratory methods, gave the following results, these being the percentages by weight:

v V Per cent. Per cent. Lead sulphide (Pb 93. 58 93. 36 Lead sulphate (PbSO4) 0.62 0. 57 Flee lead (Pb) 5.82 6.15 Free sulphur (S) 0.05 0. 05 Iron oxide (FezO;;) 0. 04 0. 03

No determinable amounts of any other metals were found, nor were there found any determinable amounts of tellurium or selenium. subject to a slight correction for experimental error.

Although material of the compositions stated may be'produced in various ways, our experience has shown that the following process will insure the most satisfactory results, viz:

Four pounds-of good commercial bar lead is melted and heated to a temperature somewhat above the melting point of the lead so as to give a very fluid molten metal.

At the same time about one pound of sulphur, either as stick sulphur, or as flowers of sulphur, and of high-grade com-- mercial quality, is melted.

The molten sulphur is poured into a container or pot which is relatively tall,- that is to say, has a small cr0ss-sectional area as compared with its capacity.

This pot or container is preferably warmed or heated so as. not tochill the sulphur. Immediately after the molten sulphur is poured into the pot, the fluid-lead is poured into the pot, and what may be termed a follower or blanket of incombusti- The analyses given above are ble material is quickly placed upon the molten material in the pot and weighted or pressed down to prevent it from being lifted by the frothing and ebullition of the mixture.

The material in the pot is allowed to cool and the cooled mass may then be broken into fragments of the desired size; These fragments consist of small crystals having a metallic lustre bedded in a porous greyish material. Some of the fragments may contain a relatively small proportion of the crystals. Such material may be discarded and only those fragments selected which have the crystalline structure well distributed through the greyish material.

Fragments of the material, selected as above described, may be inserted in the clip or holder of an ordinary detector apparatus, with the usual fine pointed cat-whisker, and will give excellent results. The contact point may be brought down on practically any point of the surface of the detector and will give good results. That is to say, little or no searching is necessary to find a sensitive spot as is the case with the ordinary crystal detector.

It has been common heretofore with crystal detectors to secure the detector in a metallic holder or cup by means of lead or other fusible metal or alloys poured into the cup or holder in a molten condition in which the crystal detector is embedded. The same method of securing the present detector may be employed, but the difliculty of this procedure may be avoided with the new detector by simply forcing the desired fragment underconsiderable pressure into a cup. It will be found that by this means the fragment will take the shape of the cup or holder. That is to say, the material acts as if it had a certain amount of malleability so that under sufficient pressure the outer portion conforms itself to the shape of the interior of the cup or holder. In this way, it becomes possible to make a good contact with the cup.

In the regular production of detectors the material may be driven into metal tubes, held against expanding by a suitable metal mold surrounding the tube. Then the metal tube with its contents, may be broken into short lengths forming disks, which are very suitable for use in a detector apparatus.

lVhile, as before stated, the detector hereinbefore described Y is particularly advantageous when used with the usual catwhisker of fine wire, it has been found that a more satisfactory result is obtained with a contact device consisting of a thin and narrow strip of sheet Zinc or aluminum; most advantageously commercially pure zinc.

In the description hereinbefore, the prodnot is described as consisting of Small crys tals bedded in a porous greyish material. This greyish material probably is a spongy lead slightly oxidized on the surface. At least this is the conclusion drawn from the apearance of the material, and from the results of the chemical analysis.

While in the foregoing we have specifically described one good method of making the detector material, it is to be understood that many variations are permissible without departing from the spirit of the invention. For example, while it is better to pour the molten lead into the molten sulphur, of course this operation may be reversed and the molten sulphur poured into the molten lead. Furthermore, the constituents may be brought together in an unmelted condition and then the mixture heated until fusion takes place. In this case it is well to provide for agitation of the mixture. However, even without agitation and with different proportions, the mixture may be melted and allowed to stratify. On cooling, it will be found that there is a stratum of the desired material which can be broken away from the remainder of the mass.

What is claimed is:

1. A detector for radio apparatus comprising a substantially complete mixture of lead sulphide and free lead.

2. A synthetic material having the property of substantially rectifying currents of radio'frequency said product, when analyzed chemically, showing a content of lead sulphide over 90 per cent by weight and a content of free lead of over 5 per cent by weight.

3. A synthetic product having the property of substantially rectifying currents of radiofrequency, said product comprising a mixture of crystals of lead sulphide and a greyish porous mass consisting principall of spongy lead intimately commingled witi said crystals.

4:. A synthetic product having the prop erty of substantially rectifying currents of radiofrequency, said product giving substantially the following analysis by weight: lead sulphide 93.36 to 93.58 per cent, lead sulphate 0.62 to 0.57 per cent, free lead 5.82 to 6.15 per cent, and the remainder being free sulphur and iron oxide (Fe O 5. The process of making a synthetic prodnot having the property of substantially rectifying radiofrequency currents. said process consisting in separately melting metallic lead and free sulphur, then pouring the two ingredients together and allowing the resulting product to cool..

6. The process of making a synthetic prod not having the property of substantially rectifying radiofrequency currents, said process consisting in pouring molten lead, heated to a temperature suflicientliy above its melting point to make it freely uid, into sulphur heated until it is fluid, covering the mixture and allowing it to cool.

7. The process of making a synthetic prodnot having the property of substantially rectifying radio frequency currents, Which consists in pouring freely fluid molten sulphur into a pot, then pouring freely fluid molten lead into the pot on top of the sulphur, immediately covering the mixture With a cover or follower in close contact with the mixture, and allowing the mixture to cool.

8. A detector device for radio apparatus comprising a piece of material comprising a substantially complete mixture of lead sulphide and a greyish porous material, consisting principally of spongy lead, said material showing an analysis of over 90 per cent lead sulphide and over 5 per cent free lead, in combination with a contact device comprising a thin strip of sheet zinc or aluminui In testimony whereof We have hereunto set our hands.

FREDERICK 1-1. I-IENDEY. RUSSELL B. EVERSON. 

